A new book offers parents a window into their kids' often tumultuous relationships with classmates

Many parents lose sleep over the riddle of their children's social life. What makes one child popular and another scorned? How can parents best foster social skills? What should a kid be taught about dealing with bullies, and when should a parent step in? These ques-tions are as old as families, but they're taking new form and fresh urgency in an era when schoolyard arguments too often get resolved with guns. A new book--Best Friends, Worst Enemies: Understanding the Social Lives of Children (Ballantine)--delves into these mysteries with uncommon sensitivity and intelligence.